34CrNiMo6钢曲轴轴颈感应淬火硬化微观机理

Microscopic mechanism of induction hardening of 34CrNiMo6 steel crankshaft journal

利用显微硬度计测试了34CrNiMo6钢曲轴轴颈在460、480、500 V淬火电压下,经中频表面感应淬火+300℃回火后的硬度值。利用光学显微镜(OM)、扫描电镜(SEM、EBSD)、X射线衍射分析仪(XRD)观察不同淬火电压下轴颈组织演变,研究了组织演变对曲轴钢表面硬度的影响机制。结果表明,在460、480、500 V电压感应淬火后,各试样表层硬度均有明显提高,并在次表层硬度达到最大。这主要是由于经不同电压表面感应淬火后,各试样不同区域组织不同,相的含量不同、位错密度不同造成的。根据组织及硬度分布的不同,轴颈由表及里可分为淬硬层、过渡层及心部。淬硬层深度、硬度与淬火电压呈正相关。

Hardness value of 34CrNiMo6 steel crankshaft journal after induction hardening with intermediate frequency and tempering at 300℃was tested under quenching voltages of 460 V,480 V and 500 V through microhardness tester.The microstructure evolution of the journal under different quenching voltages,and the influence mechanism of microstructure evolution on the surface hardness of the crankshaft steel was observed and studied by means of optical microscopy(OM),scanning electron microscopy(SEM),energy dispersive spectrometer(EBSD)and X⁃ray diffraction analyzer(XRD).The results show that after induction hardening at 460 V,480 V and 500 V,the surface hardness of each specimen is significantly improved,and the hardness of the subsurface layer reaches the maximum.This is mainly due to the different microstructure,phase contents and dislocation densities in different regions of each specimen after surface induction hardening at different voltages.According to the different structures and hardness distribution,the journal can be divided into hardened layer,transition layer and core from the surface to the inside.The depth and hardness of the hardened layer are positively correlated with the quenching voltage.